Materials characterization and adsorption isotherm data

Nano-zirconia (ZO) was synthesized using a microwave assisted one pot
precipitation route. Two biopolymers, chitosan (CTS) and carboxymethyl
cellulose (CMC), were then combined with zirconia at different w/w ratios
in order to identify the system with the most improved sorption properties
towards Pb(II), Cd(II), As(V) and F-. The formulation with 30% w/w
chitosan (ZO-CTS) was found to give enhanced uptake of F- and As(V).
Improved sorption properties could not be observed for Pb(II) and Cd(II)
in any of the ZO-polymer blends, with ZO being the most potent sorbent
here. ZO and the lead system ZO-CTS were characterized in detail using
Fourier transform infra-red spectroscopy, scanning electron microscopy,
X-ray diffraction and X-ray photoelectron spectroscopy (XPS). These
confirmed the formation of a composite system comprising nanoparticles
with 50 nm in size in which ZO was present in the amorphous form.
Interactions between Zr and the amide and hydroxide groups of chitosan
were suggested from XPS. Batch adsorption studies were carried out and
equilibrium adsorption data were fitted to a series of isotherm models. It
was observed that the combination of ZO with CTS improved the F- and As(V)
adsorption capacity most notably at pH 5.2. Fluoride adsorption by ZO-CTS
followed the Freundlich isotherm model, with an adsorption capacity of 120
mg/g. Adsorption of As(V) by ZO-CTS could be fitted with both the Langmuir
and Freundlich isotherm models, and was found to have a capacity of 14.8
mg/g. Gravity filtration studies were also carried out at two different pH
levels to test the feasibility of ZO-CTS in real-world applications. These
indicated that the sorbent could be used to filter a significant volume of
water and ensure that pollutant levels remained below acceptable values.